1. Field of the Invention
The present invention relates to an in-vehicle mount electronic controller, and particularly to an in-vehicle mount electronic controller that contains a constant-voltage power supply source for generating plural stabilized output voltages and is improved so as to comprehensively detect the presence or absence of abnormality of each output voltage and a comparison reference voltage.
2. Description of the Related Art
A constant voltage source in an in-vehicle mount electronic controller is required to generate plural stabilized output voltages. For example, a constant-voltage power supply source disclosed in JP11-265225A titled as “POWER SUPPLY DEVICE FOR ENGINE CONTROLLER” generates various output voltages, 7.8V for a converter for flash writing, 5V for a high-precision sensor and a converter for ADC (analog/digital conversion), 3.3V for a converter for CPU, 3.3V for a converter for CPU standby, and 5V for a chopper type 5V converter. The output voltage of 5V for the chopper type 5V converter is generated by ON/OFF control, and the other output voltages are generated by a continuous control dropper. This constant-voltage power supply can be designed to be compact in size and be high in efficiency, and also it can be used as a power supply for an engine controller which is suitably adaptable to requirements of the output voltage, the precision thereof, etc.
JP2001-352675A titled as “POWER SUPPLY FOR IN-VEHICLE MOUNT OPERATING EQUIPMENT” discloses a specific circuit which is supplied with power from an in-vehicle mount battery to generate stabilized output voltages of DC 5V, 3.3V, 2.7V, and it contains the description of a circuit associated with protection of over current of a transistor for controlling a constant voltage. Furthermore, JP10-288634A titled as “POWER SUPPLY VOLTAGE DETECTING CIRCUIT” discloses a power supply voltage detecting circuit including a reference voltage generating section for generating a first reference voltage and a second reference voltage lower than the first reference voltage from a power supply voltage by resistance division, an integrating section that is supplied with a voltage achieved by resistance-dividing the power supply voltage and has an output voltage having an intermediate potential between the first and second reference voltages at a stationary time, a lower limit comparator that is supplied with the first reference voltage at one terminal thereof and the output voltage of the integrating section at the other terminal thereof and detects that the power supply voltage is equal to a lower limit value or less, and an upper limit comparator that is supplied with the second reference voltage at one terminal thereof and the output voltage of the integrating section at the other terminal thereof and detects that the power supply voltage is equal to an upper limit or more. The power supply voltage detecting circuit is not required to remake a reference voltage in accordance with the specification of the power supply voltage, and detects only the rapid variation of the power supply voltage due to noise or the like.
With respect to the constant-voltage power supply source shown in JP11-265225A, there is presented a concept that the same DC 5V output voltage is separated to a small capacity power supply requiring high precision and a large capacity power supply which may be low in precision. Provision of many output voltages induces a problem that complicated processing is needed when some output voltage is abnormal. However, there is not presented a concept associated with the detection of abnormality of each output voltage. Furthermore, the constant-voltage power supply source shown in JP2001-352675A aims to prevent burnout of the constant-voltage controlling transistor due to abnormality of overcurrent, but it does not aim to accurately check the output voltage precision and thus predict occurrence of abnormality. On the other hand, the power supply voltage detecting circuit shown in JP10-288634A detects the upper and lower limit of ripple variation of the output voltage by a pair of comparison circuits, and detect variation abnormality by the logical sum of the upper and lower limits. However, the voltage as a comparison reference is a variation average value of the voltage to be detected, and thus the power supply voltage detecting circuit neither judges whether the average value itself is right nor comprehensively detects occurrence of abnormality of plural output voltages.